Mound-building termites or just mound builders are a group of termite

Termite

Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...

 species that live in mounds. This group of termites live in Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. The mounds sometimes have a diameter of 30 metres. Most of the mounds are found in well drained areas. Termite mounds usually out live the colonies themselves. If the inner tunnels of the nest are exposed it is usually dead, however, sometimes other colonies occupy a mound after the death of the original builders. The new colonizers may be of the same or a different species.

Mound Structure

The structure of the mounds can be very complicated. Inside the mound is an extensive system of tunnels and conduits that serves as a ventilation system for the underground nest. In order to get good ventilation, the termites will construct several shafts leading down to the cellar located beneath the nest. The mound is built above the subterranean nest. The nest itself is a spheroidal structure consisting of numerous gallery chambers.
They come in a wide variety of shapes and sizes. Some, like Odontotermes termites build open chimneys or vent holes into their mounds, while others build completely enclosed mounds like Macrotermes. The Amitermes(Magnetic termites) mounds are created tall, thin, wedge-shaped, usually oriented north-south.

Social Caste

Workers, smallest in size, are the most numerous of the castes. They are all completely blind, wingless, and sexually immature. Their job is to feed and groom all of the dependent castes. They also dig tunnels, locate food and water, maintain colony atmospheric homeostasis, and build and repair the nest.

The soldiers job is to basically defend the colony from any unwanted animals. When the large soldiers attack they emit a drop of brown, corrosive salivary liquid which spreads between the open mandibles. When they bite, the liquid spreads over the opponent. The secretion is commonly stated to be toxic or else undergoes coagulation with the air, which renders it glue-like.

Finally, there are the reproductives. They include the king and the queen. The queen can sometimes grow up to six centimetres long while the lower classes are generally less than one centimetre.